This shaft sealing device is particularly adaptable to machines, such as screw conveyors, mixers, blenders, pumps and other processing equipment handling liquids, dry solids and slurries and having in common a rotating shaft communicating through the confining wall of a vessel.
In its simplest form (FIG. 1), it is a cylindrical cartridge comprised of a housing; an elastomeric, fluid-filled, self-contained compression ring; compartment spacers, which may be drilled to allow passage of a pressurized lubricant into the cartridge; mechanical packing of any variety which intervenes between the fluid-filled ring and the rotating shaft; and an externally adjustable gland follower. The cartridge is mounted radially over the rotating shaft and provides a means of applying uniform radial force to the intervening packing without the necessity of an external source of fluid pressure, as is common in diaphragm-type seals.
The method of fabricating the monolithic fluid-filled compression ring is novel in that advantage is taken of the volume change which occurs when selected organic fluids are cooled to sub-zero temperatures and atmospherically reheated to ambient temperatures.
Polyaromatic compounds, modified esters and dextrose solutionsare typical of the organic materials employed.
FIG. 2, is a representation of the individual shapes of the components in the compressed state.
In a second form (FIG. 3), the compartment spacers form a contiguous multiple compartment seal with each compartment subjected to equal radial pressures imposed by the gland follower.
In a third form (FIG. 4), the compartment spacers are hollow metallic or polymer rings, having an inlet and outlet tube to permit simultaneous cooling of the in-contact elastomeric fluid-filled ring and the mechanical packing. The rotating, heat conducting shaft metal, is coincidently cooled.
In a fourth form the compartment spacers are common lantern rings to provide a means for continuous flushing of the individual compartments of a single or multiple compartment seal.
Hitherto, shafts have been sealed by means of conventional stuffing boxes, including mechanical packings consisting of annular gaskets compressed by annular gland followers moved axially against the packing, thereby converting axial force to radial components of force. A large proportion of the axial force is consumed in compression of the mechanical packing. Mechanical packing takes the shape of the restraining container and is subjected to deformation due to eccentric rotation of the shaft. The resulting phenomena is termed "pumping the seal".
The second generation in development of conventional stuffing boxes included pressurized diaphragms having an independent source of fluid pressure, usually fluid from the discharge side of a pump or an air compressor. The diaphragm seals proved unsatisfactory for several reasons: (a) sealing pressure failed during power failures; (b) temperature tends to build up due to frictional heat, thus thermally expanding the enclosed fluid in an uncontrollable manner; (c) mechanical arrangement of the seals did not permit flushing or lubrication of the shaft at the packing interface.